About 2 gun shows ago I picked up a bunch of HANDLOADER magazines. Anyway mag # 125 July-August 1987 has a serious article on standard deviation. It seems that all these gun magazine "egg-spurts" have got it all wrong. The point he brings out is,"Standard deviation measure VARIABILITY (emphasis is the authors) of the average. That is exactly what it is supposed to do; but for shooters, the result can be misleading if it is used to compare velocities (or any other kinds of values) of different magnitudes."
This article gets a bit complicated, but if you can chase down a copy,(try Wolfe Publishing) it makes for some enightening reading.
Paul B.